The payback period obviously depends on the cost of the turbine and installation as well as the amount of energy generated. Further, since the market is still relatively immature there is little real data available. However, payback periods are estimated to be around 10 or more years.

• Energy and Carbon savings

A 6kW system can provide 12,000-15,000kWh or units of electricity, reducing carbon dioxide emissions by 5-7 tonnes per year.

To increase the cost-effectiveness of the turbines and the amount of energy saved, a method of energy storage, such as an electric immersion heating element in a water tank, should be used. This will help ensure that all of the electricity generated by the wind turbine is matched by the load of the household.

Typically, a household sees a reduction of between a quarter and a third in its annual electricity bill.

• Sell-back agreements

In order to realise extra value from a turbine installation it is possible to sign either an export arrangement or a buy & sell back arrangement with a complying electricity supply company. However, these agreements may require that you get accredited for the various benefits of renewable generation such as ROCs. In order to claim these benefits an Ofgem accredited total generation meter must be fitted increasing the cost of the installation. The type of agreement will depend on your local electricity company.

Wind energy has the benefit of counting towards the Renewables Obligation targets, introduced in April 2002. This is a legal requirement placed on electricity supply companies to source an increasing proportion of their supply from renewable resources up to 10% by 2010, and increasing to 15% by 2015. If your generation capacity is sufficiently large and is ‘supplied’ onwards, i.e. distributed through a network, you may be able to claim ROCs. In 2004, generators less than 50kW were included in the RO and therefore have the opportunity to claim ROCs, the minimum required power output is 0.5 megawatt hours per annum. The market value of a ROC varies with time but is around 3.2 pence per kWh, in addition to any payment for the electricity itself.

Unfortunately, there is currently no mechanism for getting paid for electricity exported to the grid, or for claiming Renewable Obligation Certificates (ROCs). Although typically the control panels of turbines display indicative values of kWh produced, but this is not sufficient for DNOs to credit electricity payments or claim ROCs